Abstract 2189: The role of generational obesity on the ovarian metastatic niche

Obesity is a worldwide epidemic associated with many cancer types due to persistent inflammation, hyperglycemia and hyperinsulinemia providing an abundance of nutrients and growth factors to cancer cells resulting in an ideal microenvironment. Maternal obesity often results in an increased risk of offspring developing obesity. Chronic inflammation and immunosuppression found in obese patients have been linked to ovarian cancer (OvCa). OvCa is the most lethal gynecological malignancy among women and approximately 12% of OvCa patients are obese. Poor survival rates are attributable to women presenting with advanced disease with disseminated intraperitoneal (i.p) metastasis at diagnosis. Metastatic tumor cells shed from the primary tumor and preferentially home to the mesothelium of the omentum and other peritoneal organs producing secondary lesions. Developmental programming suggests that perinatal nutritional influences can alter gene expression in offspring. A pre-clinical murine model of diet-induced obesity that included maternal cohorts of C57BL/6 mice (dam) with intact host immunity fed either a control diet (CD; 10% fat) or a high-fat diet (HFD; 40% fat) and the resulting offspring fed either diet was utilized to explore diet induced genetic and physical modifications. Body composition analysis revealed differences in weight and lean mass was dependent on offspring diet alone and fat mass was dam diet dependent among CD fed offspring. Second harmonic generation microscopy demonstrated a larger area of collagen mesh-work between fenestrations in the omentum of HFD fed mice as well as an increase in anisotropy. Additionally, a tumor study was performed using either CD or HFD fed offspring to quantify site-specific metastatic success to the adipose-rich tissues of the peritoneal cavity. Mice were injected i.p. with fluorescently tagged syngeneic ID8 murine OvCa cells and disease progression was tracked for 8 weeks. Abdominal organs were dissected, imaged, and organ-specific tumor burden quantified. Overall, offspring fed a HFD displayed an increase in organ-specific tumor burden relative to offspring fed a CD, regardless of dam diet. Furthermore, HFD offspring from HFD dams displayed higher omental tumor burden than HFD offspring from CD dams. In addition, HFD fed mice accumulated more ascites fluid than CD fed mice, however variances were independent of dam diet. Comparison of ascites cytokine expression revealed CXCL13, a dominant chemokine in adipocytes, was significantly increased in mice only exposed to a HFD suggesting an additive effect of both maternal and offspring obesity. Interestingly, increased CXCL13 expression has been reported in OvCa cell lines and in clinical samples. Together, the results suggest maternal obesity or subsequent exposure to a HFD can influence ovarian cancer metastasis.

Citation Format: Tyvette Hilliard, Phillip Petrasko, Yueying Liu, Jing Yang, Marwa Asem, Jeff Johnson, Gifty Marfowaa, Brooke Kowalski, Elinor Schnautz, Morgan McCabe, M. Sharon Stack. The role of generational obesity on the ovarian metastatic niche [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2189.

Host Mesothelin Expression Increases Ovarian Cancer Metastasis in the Peritoneal Microenvironment

Mesothelin (MSLN), a glycoprotein normally expressed by mesothelial cells, is overexpressed in ovarian cancer (OvCa) suggesting a role in tumor progression, although the biological function is not fully understood. OvCa has a high mortality rate due to diagnosis at advanced stage disease with intraperitoneal metastasis. Tumor cells detach from the primary tumor as single cells or multicellular aggregates (MCAs) and attach to the mesothelium of organs within the peritoneal cavity producing widely disseminated secondary lesions. To investigate the role of host MSLN in the peritoneal cavity we used a mouse model with a null mutation in the MSLN gene (MSLN^KO). The deletion of host MSLN expression modified the peritoneal ultrastructure resulting in abnormal mesothelial cell surface architecture and altered omental collagen fibril organization. Co-culture of murine OvCa cells with primary mesothelial cells regardless of MSLN expression formed compact MCAs. However, co-culture with MSLN^KO mesothelial cells resulted in smaller MCAs. An allograft tumor study, using wild-type mice (MSLN^WT) or MSLN^KO mice injected intraperitoneally with murine OvCa cells demonstrated a significant decrease in peritoneal metastatic tumor burden in MSLN^KO mice compared to MSLN^WT mice. Together, these data support a role for host MSLN in the progression of OvCa metastasis.

Ascites-induced compression alters the peritoneal microenvironment and promotes metastatic success in ovarian cancer

The majority of women with recurrent ovarian cancer (OvCa) develop malignant ascites with volumes that can reach > 2 L. The resulting elevation in intraperitoneal pressure (IPP), from normal values of 5 mmHg to as high as 22 mmHg, causes striking changes in the loading environment in the peritoneal cavity. The effect of ascites-induced changes in IPP on OvCa progression is largely unknown. Herein we model the functional consequences of ascites-induced compression on ovarian tumor cells and components of the peritoneal microenvironment using a panel of in vitro, ex vivo and in vivo assays. Results show that OvCa cell adhesion to the peritoneum was increased under compression. Moreover, compressive loads stimulated remodeling of peritoneal mesothelial cell surface ultrastructure via induction of tunneling nanotubes (TNT). TNT-mediated interaction between peritoneal mesothelial cells and OvCa cells was enhanced under compression and was accompanied by transport of mitochondria from mesothelial cells to OvCa cells. Additionally, peritoneal collagen fibers adopted a more linear anisotropic alignment under compression, a collagen signature commonly correlated with enhanced invasion in solid tumors. Collectively, these findings elucidate a new role for ascites-induced compression in promoting metastatic OvCa progression.

Host Wnt5a Potentiates Microenvironmental Regulation of Ovarian Cancer Metastasis

The noncanonical Wnt ligand Wnt5a is found in high concentrations in ascites of women with ovarian cancer. In this study, we elucidated the role of Wnt5a in ovarian cancer metastasis. Wnt5a promoted ovarian tumor cell adhesion to peritoneal mesothelial cells as well as migration and invasion, leading to colonization of peritoneal explants. Host components of the ovarian tumor microenvironment, notably peritoneal mesothelial cells and visceral adipose, secreted Wnt5a. Conditional knockout of host WNT5A significantly reduced peritoneal metastatic tumor burden. Tumors formed in WNT5A knockout mice had elevated cytotoxic T cells, increased M1 macrophages, and decreased M2 macrophages, indicating that host Wnt5a promotes an immunosuppressive microenvironment. The Src family kinase Fgr was identified as a downstream effector of Wnt5a. These results highlight a previously unreported role for host-expressed Wnt5a in ovarian cancer metastasis and suggest Fgr as a novel target for inhibition of ovarian cancer metastatic progression.Significance: This study establishes host-derived Wnt5a, expressed by peritoneal mesothelial cells and adipocytes, as a primary regulator of ovarian cancer intraperitoneal metastatic dissemination and identifies Fgr kinase as novel target for inhibition of metastasis.

Abstract 5005: Aging promotes changes to peritoneal and omental collagen structure that contribute to increased ovarian cancer metastatic success

Ovarian cancer (OvCa) is the deadliest cancer of the female reproductive system, ranking fifth in overall cancer deaths among women. Unlike the majority of cancers, OvCa metastasizes via diffusion through the peritoneal cavity, resulting in multiple metastatic sites, including the omentum and peritoneum. These metastasizing OvCa cells induce rapid mesothelial cell retraction and readily adhere to the sub-mesothelial collagen of the extracellular matrix. Epidemiologic data identifies age as a significant risk factor in OvCa, as about half of diagnoses are in women over the age of 63. Despite this, age is understudied in the OvCa field. Using a C57Bl/6 mouse model of aging, young (Y) mice ranging from 3-6 months of age, and aged (A) mice ranging from 20-23 months of age, corresponding to women aged 20-30 years (Y) and 60-67 years (A) were used to study the role aging has on metastasis. Fluorescently tagged C57Bl/6 syngeneic ID8 p53-/- mouse OvCa surface epithelial cells were injected intraperitoneally in young and aged mice and disease progression was evaluated for 5.5 weeks. Organ-specific tumor burden was quantified with ImageJ, revealing increased tumor burden in aged mice compared to their young counterparts. These results were reproduced in the FVB mouse model using syngeneic PTENshRNA/KRASG12V modified FVB OvCa oviductal epithelial cells. Second Harmonic Generation Microscopy (SHG) was used to visualize collagen of the peritoneal and omental tissues from young and aged C57Bl/6 mice. Distinct structural differences were shown in omental collagen in the Y vs A cohorts and validated with Scanning Electron Microscopy (SEM). Additionally, Nanoindentation illustrated mechanical differences between young and aged peritoneal samples. In conclusion, aging induces changes in the structure and mechanical strength of peritoneal and omental collagen, which contribute to OvCa metastasis.

Citation Format: Elizabeth Harper, Elizabeth Loughran, Annemarie Leonard, Tyvette Hilliard, Marwa Asem, Yueying Liu, Jing Yang, Yuliya Klymenko, Jeff Johnson, Emma Sheedy, Zonggao Shi, Matthew Leevy, Matthew Ravosa, M. Sharon Stack. Aging promotes changes to peritoneal and omental collagen structure that contribute to increased ovarian cancer metastatic success [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5005.

Abstract 4511: The role of Wnt5a signaling pathway in epithelial ovarian cancer progression

Ovarian cancer (OvCa) is the most fatal gynecologic malignancy and the 5th leading cause of cancer death among U.S. women. The majority of women with OvCa (75%) have a very low survival rate (30%), as OvCa is usually diagnosed in late stages after development of intraperitoneal metastasis. Thus, it is indispensable to understand the molecular mechanisms that contribute to OvCa metastatic success, in order to design effective treatment strategies to improve the overall survival of women with OvCa. Wnt5a is a noncanonical Wnt ligand that binds to several cell membrane receptors and activates many downstream signaling pathways that are fundamental for normal developmental processes during embryogenesis. In the past decade, the aberrant activation or inhibition of Wnt5a signaling is emerging as an important event in cancer progression, exerting both oncogenic and tumor-suppressive effects. The role of Wnt5a in OvCa is controversial, as studies report conflicting data. In addition, mechanistic data regarding the contribution of Wnt5a to OvCa progression are largely unavailable. The main aim of this research is to obtain a molecular-level understanding of Wnt5a signaling in OvCa and to investigate its potential roles in influencing OvCa metastatic success. Our data show Wnt5a is prevalent in ascites samples from women in different stages with OvCa, suggesting a role for Wnt5a in promoting disease progression. Data obtained from TCGA (n=583) show high expression of Wnt5a in primary ovarian tumors. Furthermore, Wnt5a enhanced OvCa cells adhesion, migration and invasion in a panel of organotypic and ex vivo functional assays. This was combined with striking morphologic changes characteristic of an invasive phenotype in OvCa cells treated with recombinant Wnt5a protein and formation of tunneling nanotubes (TNT). Overall, our data suggest that Wnt5a plays an oncogenic role in epithelial ovarian cancer cells. More experiments exploring Wnt5a activated pathways and effects in epithelial ovarian cancer cells are under way.

Citation Format: Marwa Asem, Allison Young, Carlysa Oyama, Rebecca Burkhalter, Steven Buechler, Daniel Miller, Sharon Stack. The role of Wnt5a signaling pathway in epithelial ovarian cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4511.

Aging Increases Susceptibility to Ovarian Cancer Metastasis in Murine Allograft Models and Alters Immune Composition of Peritoneal Adipose Tissue

Ovarian cancer, the most deadly gynecological malignancy in U.S. women, metastasizes uniquely, spreading through the peritoneal cavity and often generating widespread metastatic sites before diagnosis. The vast majority of ovarian cancer cases occur in women over 40 and the median age at diagnosis is 63. Additionally, elderly women receive poorer prognoses when diagnosed with ovarian cancer. Despite age being a significant risk factor for the development of this cancer, there are little published data which address the impact of aging on ovarian cancer metastasis. Here we report that the aged host is more susceptible to metastatic success using two murine syngeneic allograft models of ovarian cancer metastasis. This age-related increase in metastatic tumor burden corresponds with an increase in tumor infiltrating lymphocytes (TILs) in tumor-bearing mice and alteration of B cell-related pathways in gonadal adipose tissue. Based on this work, further studies elucidating the status of B cell TILs in mouse models of metastasis and human tumors in the context of aging are warranted.

Multiparity activates interferon pathways in peritoneal adipose tissue and decreases susceptibility to ovarian cancer metastasis in a murine allograft model

Ovarian cancer is the fifth leading cause of cancer deaths in U.S. women and the deadliest gynecologic malignancy. This lethality is largely due to the fact that most cases are diagnosed at metastatic stages of the disease when the prognosis is poor. Epidemiologic studies consistently demonstrate that parous women have a reduced risk of developing ovarian cancer, with a greater number of births affording greater protection; however little is known about the impact of parity on ovarian cancer metastasis. Here we report that multiparous mice are less susceptible to ovarian cancer metastasis in an age-matched syngeneic murine allograft model. Interferon pathways were found to be upregulated in healthy adipose tissue of multiparous mice, suggesting a possible mechanism for the multiparous-related protective effect against metastasis. This protective effect was found to be lost with age. Based on this work, future studies exploring therapeutic strategies which harness the multiparity-associated protective effect demonstrated here are warranted.

Abstract TMEM-025: IMPACT OF MESOTHELIN EXPRESSION ON THE METASTATIC SUCCESS OF OVARIAN CANCER

Ovarian cancer is the most lethal gynecological cancer in U.S. women. Poor 5-year survival rates (<30%) are due to presentation of most women at diagnosis with advanced stage disease with widely disseminated intraperitoneal metastasis. However, when diagnosed before metastatic propagation the overall 5-year survival rate is >90%. Metastasizing tumor cells grow rapidly and aggressively attach to the mesothelium of all organs within the peritoneal cavity, including the parietal peritoneum and the omentum, producing secondary lesions. Mesothelin (MSLN), a 40kDa glycoprotein that is over expressed in many cancers including ovarian and mesotheliomas is suggested to play a role in cell survival, proliferation, tumor progression and adherence. However, the biological function of mesothelin is not fully understood as MSLN knockout mice do not present with an abnormal phenotype. Conversely, MSLN has been shown to bind to the ovarian cancer antigen, CA-125, and thought to play a role in the peritoneal diffusion of ovarian tumor cells. Taking into consideration the potential importance of MSLN/CA-125 binding in ovarian tumor metastasis within the peritoneum, MSLN wild type (WT) and knockout (KO) mice were used to explore the role of mesothelin on the susceptibility of ovarian tumor cells to adhere to the mesothelium of the organs in the peritoneal cavity. An ex vivo peritoneal assay, using CA-125 positive human ovarian tumor cells OVCAR8-GFP and peritoneal explants from MSLN WT and KO mice demonstrated a decrease in OVCAR8-GFP cell adhesion to peritoneal tissues from MSLN KO mice compared to MSLN WT mice. Furthermore, allograft tumor studies using MSLN WT and KO mice injected intraperitoneally with fluorescently-tagged syngeneic murine ovarian cancer cells (ID8-RFP) was performed. Disease progression was evaluated post injection by fluorescent in vivo imaging prior to end point dissection (~8 weeks). Abdominal organs were dissected, imaged ex vivo and organ-specific tumor burden was quantified by tumor area. Tumor burden was significantly decreased in the liver and omentum of MSLN KO mice compared to MSLN WT mice. Together, the results demonstrate a loss of mesothelial cell-ovarian tumor cell adhesion in the omentum and peritoneum of mice that do not express MSLN.

Citation Format: Tyvette Hilliard, Kyle Iwamoto, Elizabeth Loughran, Marwa Asem, Yueying Liu, Jing Yang, Laura Tarwater, Yuliya Klymenko, Jeff Johnson, Zonggao Shi, and M. Sharon Stack. IMPACT OF MESOTHELIN EXPRESSION ON THE METASTATIC SUCCESS OF OVARIAN CANCER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr TMEM-025.

Abstract TMEM-029: AGING INCREASES SUSCEPTIBILITY TO OVARIAN CANCER METASTASIS IN A MURINE ALLOGRAFT MODEL

Ovarian cancer (OvCa) is the leading gynecological malignancy in women in the United States. OvCa metastasizes uniquely, spreading through the peritoneal cavity and generating widespread metastatic sites. The vast majority of OvCa cases occur in women over 40 and the median age at diagnosis is 63 (SEER). Despite age being a significant risk factor for the development of OvCa, there is a paucity of studies addressing the role of aging in OvCa metastasis. To our knowledge, there are no reports utilizing old mice to investigate the effects of age on metastasis in vivo. We designed a study using a C57BL/6 model of aging where young (Y) mice are 3-6 months of age and aged (A) mice are 20-23 months of age, corresponding to young (20-30 years) and aged (60-67 years) humans. Using the C57BL/6 syngeneic ID8 mouse ovarian surface epithelial cell line, we tested the effect of aging on metastatic success in vivo. An allograft study was carried out with Y and A mice that were intraperitoneally injected with 3.7x106 ID8 RFP-tagged cells. The mice were imaged once a week starting at 4.5 weeks post injection and were sacrificed for dissection at 8 weeks post injection. Live imaging suggested OvCa metastasis was more efficient in the aged animals than in the young animals. After dissection, the abdominal organs were imaged ex vivo and tumor burden was quantified. The aged mice displayed heavier tumor burden in the gonadal fat compared to the young. Interestingly, no difference in metastasis to the omentum was detected. To investigate why gonadal fat is more receptive to metastasis in the aged animals, periovarian adipose from 4 young and 4 aged healthy non-tumor bearing mice was isolated for RNAseq analysis. Several immune pathways involving B cells were found to be significantly upregulated in the RNA from aged animals. Studies will be conducted to elucidate the status of B cells in aging periovarian adipose, including immunohistochemistry for CD45 and other B cell markers upregulated in the RNAseq dataset.

Citation Format: Elizabeth Loughran, Annemarie Leonard, Ryan Phan, Laura Tarwater, Tyvette Hilliard, Marwa Asem, Yueying Liu, Jing Yang, Yuliya Klymenko, Jeff Johnson, Zonggao Shi, Matthew Leevy, Matthew Ravosa and M. Sharon Stack. AGING INCREASES SUSCEPTIBILITY TO OVARIAN CANCER METASTASIS IN A MURINE ALLOGRAFT MODEL [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr TMEM-029.

Abstract B67: The impact of parity on the metastatic success of ovarian cancer

Ovarian cancer is the most fatal gynecological cancer. Epithelial ovarian cancer (OvCa), the most common subtype, usually goes undetected until metastatic and often fatal stages of the disease. OvCa follows a unique form of metastasis, spreading through the peritoneal cavity and forming metastatic sites on the peritoneum. Epidemiologic data suggest that child-bearing, or parity, reduces a woman's risk of developing ovarian cancer, with more births providing greater protection. Despite the association of parity with a decreased incidence of ovarian cancer, very few studies have explored the relationship between parity and metastatic success. A recent study compared metastatic success to the omentum in 12-month-old C57Bl/6 retired breeders and 5-month-old virgin mice, reporting that parous mice are less susceptible to metastasis due to the parity-associated differences in the immune compositional profile in the omental fat band (Cohen et al. 2013). This tumor study compared mice of different ages and did not report specific numbers of pregnancies. To further investigate the role of parity number in OvCa metastasis, we designed a study that controls for age and compares mice with specific parity number. Three age-matched C57Bl/6 groups were evaluated: nulliparous (V), parous 1 (P1), and parous 3 (P3) mice. We tested the effect of parity on metastatic success in vivo with an allograft study using the C57Bl/6 syngeneic ID8 mouse ovarian surface epithelial cell line. ID8 ovarian cancer cells (106) were injected into the peritoneal cavity of V, P1 and P3 mice. In contrast to the results of Cohen at al. that utilized a different syngeneic ovarian cancer cell line, we found no significant difference in metastasis to the omentum in the parous animals, but significantly reduced metastasis to the fat-enveloped ovaries and visceral fat pads in the P3 mice. This suggests that the visceral fat adjacent to the uterus and ovaries in multi-parous animals is a unique environment, resilient to metastasis. Factors in fat tissue responsible for this phenomenon are being investigated.

Citation Format: Elizabeth A. Loughran, Ryan Phan, Annemarie K. Leonard, Laura Tarwater, Marwa Asem, Yuliya Klymenko, Yueying Liu, Jing Yang, Jeff Johnson, Matthew Ravosa, M. Sharon Stack. The impact of parity on the metastatic success of ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B67.